BLOCKCHAIN
No central authority in control
No need to trust your counterpart to perform their
obligations or properly record transactional data
Game Theory is used to model incentives
Cryptography guarantees security as well as privacy

PACTA SUNT SERVANDA

A smart contract is a computerized
transaction protocol that executes the
terms of a contract.
â&#x20AC;&#x201D; Nick Szabo, Smart Contracts, 1994

SMART CONTRACTS
The blockchain acts as a Virtual
Machine
Cryptographically stored
Operate autonomously
Tipically, have a long lifetime

Solidity is a contract-oriented, high-level language for
implementing smart contracts over the Ethereum
Virtual Machine

THREE GOVERNANCE SCENARIOS

Blockchain Ecosystem

OpenStack

Identity

Keystone

Certificate Authority

Barbican

Node Ledger Storage

Cinder / Swi

Stack Management

Heat

DNS

Designate

Adapted from Blockchain and OpenStack - Building Trusted Chains

SCENARIO #1: IMMUTABLE AUDIT TRAIL

Chainpoint is an open standard for linking data to the
blockchain to create a timestamp proof

Source: Chainpoint.org

The Keystone middleware library is able to audit API
requests for each component of OpenStack

Source: OpenStack.org

Pros

Cons

Simplicity
Cost
eﬀectiveness

Needs a trade-oﬀ between on- and
oﬀ-chain data in case of heavy
logging

SCENARIO #2: BILLING FOR CLOUD
RESOURCES

Pros

Cons

Smart contracts are used to
enforce payments
Fine control of resource
consumption

VAT regulations for
cryptocurrencies

SCENARIO #3: SMART GOVERNANCE

Using smart contracts to orchestrate the cloud by
calling the Heat API.
This is the most challenging scenario.

CAVEAT: Most blockchains (e.g., Ethereum) are
designed to be entirely deterministic.
Hence making API calls from inside a smart contract
(e.g., a Solidity program) is forbidden.

FIRST SOLUTION: We accept data inputs from more
than one untrusted party and then execute the datadependent action only a er a number of them have
provided the same answer.
INEFFICIENT

SECOND SOLUTION: We demonstrate that the data is
genuine and untampered (auditable VMs, Trusted
Execution Environments, ...).

Oracles (e.g., Oraclize) can act as data carriers,
building a reliable connection between APIs and the
smart contract
And we can build others.

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